Historically, food products in the half product stage were prepared in Oriental countries from starchy root vegetables, particularly cassava, the half products being desirable because they can be stored under room temperature conditions. In more recent times, the techniques employed early in the Orient have become popular for preparing half products from potato starch or potato flour. A significant advance in the art of marking food half products occurred when Wayne W. Campfield developed the method disclosed in U.S. Pat. No. 3,150,978. According to that method, a raw starch-containing material, ranging from "corn flour" to potatoes or tapioca, is combined with water to form a dough, the dough is cooked while being worked in order to gelatinize the starch content, the cooked dough is then cooled while confined, the cooled dough is then extruded and cut into pieces under conditions such that the pieces will not expand significantly, and the pieces are then dried. More recently, special plant equipment has been made available to the snack food trade by Mapimpianti S.P.A., Galleria, Italy; Creuset-Loire, Firminy, France and Wenger Mfg. Co., Sabetha, Kansas, and the new equipment has enabled the trade to achieve relatively high speed production of half products for snack foods and the like.
As the art of making half products for snack foods and the like progressed, specifications for the products became increasingly severe. Thus, while early snack foods were typified by so-called "corn chips", the demand soon increased to products of relatively complex, precisely predetermined shape, such as fish shapes, wagon wheels, grids, helices, etc. And the extent of expansion, comparing the half product to the final puffed product, progressively increased so that a marketable half product now must puff to at least about twice its size. Then, despite the increasing complexity of the shapes, it became necessary to achieve by puffing an expansion which is uniform throughout the piece. Finally, increasingly strict requirements have arisen as to texture, mouth feel and flavor. In order to meet such increasingly strict specifications, the trade has adopted potato flour, potato starch and tapioca as the sources of dextrinizable starch and has come to rely on frying in oil as the method for puffing the half product.
The increasing popularity of puffed snack foods and like products has created a demand for an acceptable half product in which the starch material is at least predominantly from corn. So long as the product was of a simple shape and extensive puffing was not required, products have been produced by following the general teachings of Campfield U.S. Pat. No. 3,150,978. However, even with the advent of the improved production apparatus now available for making half products, the trade has not produced a corn half product which would satisfy today's market requirements. We have concluded that at least some of the difficulties encountered in prior-art efforts to make modern day puffable half products from corn have arisen from the fact that prior to, e.g., 1970, such raw materials as "corn flour" had a complex and unpredictable makeup which, though satisfactory for ordinary cooking and baking purposes, is not satisfactory for making half products of complex shape and which must have a high degree of puffability. Thus, the then-available dry milled corn flours resulted from combining all of the flour streams of the mill into a single bin, so that the "corn flour" was a combination of rebolt flour and reduction flour, with perhaps other flour fractions and minor proportions of non-flour materials. Though such flours can be used to make a half product, the resulting half product will not puff to the extent required by today's market, puffing will not be uniform throughout the piece, and the eating qualities will not satisfy today's standards when the half product is of complex shape.